"Electrotransport" refers generally to the passage of a substance through a substrate, such as skin, mucous membrane, or nails, induced by application of an electrical potential. For example, a beneficial therapeutic agent may be introduced into the human body by electrotransport. One type of electrotransport, electroosmosis, involves the movement of a liquid out of or through a synthetic or biological membrane under the influence of an electric field. A more widely used electrotransport process, iontophoresis, involves the electrically induced transport of charged ions. Another type of electrotransport, electroporation, involves the transport of an agent through transiently-existing pores formed in the substrate under the influence of an electric field. However, in any given electrotransport process, more than one of these processes may be occurring simultaneously to a certain extent.
Accordingly, "electrotransport", as used herein, should be given its broadest possible interpretation so that it includes the electrically induced or enhanced transport of at least one agent, which may be charged, uncharged, or mixtures thereof, regardless of the specific mechanism or mechanisms by which the agent actually is transported.
Electrotransport devices generally use at least two electrodes which are in electrical contact with some portion of the skin, nails, mucous membrane, or other surface of the body. One electrode, commonly referred to as the "donor" or "active" electrode, is the electrode from which the agent is delivered into the body. The other electrode, typically termed the "counter" or "return" electrode, serves to close the electrical circuit through the body. For example, an agent to be delivered is positively charged, i.e. a cation, then the anode will be the active or donor electrode, while the cathode serves to complete the circuit. Alternatively, if an agent is negatively charged, i.e. an anion, the cathode will be the donor electrode. Additionally, both the anode and cathode may be considered donor electrodes if both anionic and cationic agent ions are to be delivered.
Furthermore, electrotransport delivery devices generally require at least one reservoir or source of the agent to be delivered to the body. Examples of such donor reservoirs include a pouch or cavity as described in Jacobsen, U.S. Pat. No. 4,250,878, a porous sponge or pad as disclosed in Jacobsen et al, U.S. Pat. No. 4,141,359, and a pre-formed gel body as described in Webster, U.S. Pat. No. 4,383,529, which are herein incorporated by reference. Such donor reservoirs are electrically connected to, and positioned between, the anode or cathode and the body surface, to provide a fixed or renewable source of one or more agents or drugs. In addition, electrotransport delivery devices have an electrical power source, some having an electrical controller designed to regulate the rate of drug delivery. Other optional elements include rate-controlling membranes, insulating members, and protective backing members.
Since the individual elements in an electrotransport device may have differing life cycles, electrotransport devices may be designed to be distributed in two general components, one being a disposable component and the other being a reusable component. For example, the drug or other beneficial agent contained in the donor reservoir may be depleted long before the completion of the useful life of certain hardware used in the device such as the power source or electrical controller. In this case, the disposable component may contain an agent reservoir and the reusable component may contain an electrical controller component and/or an electrical power source. In another example, the power source may be a battery having a limited life cycle, while the electrical controller contains long-lasting solid state circuitry. Here, the battery may be placed in the disposable component, while the electrical controller is placed in the reusable component. Although there are numerous element combinations which may be envisioned in each of the disposable and reusable components, a "reusable component", as that term is used herein, refers to one component of a electrotransport device whose useful life exceeds that of a second component, referred to herein as a "disposable component", wherein the two components may be separated so that the reusable component may subsequently be reused while the disposable component is discarded and replaced with another disposable component. In general, the reusable and disposable components are mated to one another, by mechanical and/or electrical connections, in order to form a complete electrotransport device, which device is then adapted to be placed in agent transmitting relation with the body surface (e.g., skin or mucosal membrane) of a patient. Exemplary of electrotransport delivery devices having reusable and disposable components are those disclosed in U.S. Pat. Nos. 4,865,582; 4,950,229 (see column 8, lines 38-40); and 5,037,381.
U.S. Pat. No. 4,865,582 (Sibalis) discloses an electrically powered transdermal drug applicator having a reusable power supply and a disposable drug reservoir. In one embodiment (see FIG. 2A), the drug reservoir has an adherent surface 13 which presumably has a release liner (similar to liner 48) affixed thereto prior to device assembly. In order to assemble the device, the end user peels off the release liner, then applies the adherent surface of the disposable drug reservoir to the reusable power supply/controller 54. The release liner is intended to mask or protect the adhesive prior to assembly of the device and is removed prior to alignment of the reusable and disposable components. Unfortunately it is sometimes difficult to precisely align the controller 54 with the disposable component during mating of the two components. This problem is exacerbated by the adhesive 13 which can cause the disposable and reusable components to mate in a misaligned configuration. Hence, misalignment and premature adhesion of the components may occur with this device assembly. Realignment after premature adhesion is aggravating to the end user, at a minimum, and may also cause damage to the adhesive or drug reservoir.
In order to assemble an electrotransport device having two components designed to be adhesively mated, with or without other mechanical connectors, the user must align the reusable component to the disposable component and optionally make the appropriate mechanical and/or electrical connections. The devices of the prior electrotransport art are prone to misalignment of the reusable and disposable components. This misalignment is difficult, if not impossible to correct, particularly once the misaligned components have become adhesively bonded together. This misalignment of components can adversely affect the operation of the assembled electrotransport device.